Not getting a full tank of fuel with a new car is really cheap behaviour, imho. Especially if they’re expecting to get the annual Servicing work.
I’ve mentioned before that my first car was on fumes when I drove it away, having been assured I’d get it with a full tank, and it was only because I took it across the road for a quick refresher drive first that I didn’t end up stuck on the ring-road. If I’d had the confidence I would have gone back to the showroom and kicked up a very public stink.